class A(object):
    def __init__(self):
        print('A')


class B(A):
    # def __init__(self):
    #     print('B')
    pass

class C(A):
    # def __init__(self):
    #     print('C')
    pass

class D(B,C):
    # def __init__(self):
    #     print('D')

    pass



c = D()